This Application claims the benefit of Korean Application No. 00-29299, filed on May 30, 2000 and Korean Application No. 00-33839 filed on Jun. 20, 2000, in the Korean Industrial Property Office, the disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical disc write apparatus and a method therefor, and more particularly, to an apparatus protecting the header region of an optical disc and a method therefor, by which it is possible to prevent a signal from being overwritten in a header of the optical disc when the signal is written on the optical disc.
2. Description of the Related Art
A DVD-RAM is a system for writing a signal on an optical disc and reproducing a signal from an optical disc. The optical disc used for the system is divided into a plurality of sectors, each of which consists of a header region and a write region. Overwriting is not allowed in the header region of the optical disc during repetitive writing and reproducing processes. The repetitive writing function of the DVD-RAM can be realized using the data region of the optical disc, on which data can be repetitively written and reproduced. However, since the header region and the write region of the optical disc used for the DVD-RAM are formed of a material on which data can be written, a write apparatus must be controlled so that data is not overwritten in the header region when data is repetitively written.
However, when data is written on the DVD-RAM disc, the data can be overwritten in the header region. Accordingly, a corresponding sector cannot often be used. Representative factors are as follows. First, when the length of a write clock period used for making a write control signal (a write gate) for turning on and off the output of a write laser beam is greater than a normal length of the write clock, data can be written in the header region of the next sector after the data is written in the data region and the buffer region of a current sector. Second, data can be overwritten in the header region since a jump from a zone where data is currently written to other zones can occur due to a disturbance or other factors. Third, data can be overwritten in the header region when a write clock is generated using fixed crystal (X-tal) that cannot sense change in the rotation speed of a disc, and the rotation speed of a spindle motor is excessively high.
Further, a data region of the optical disc often cannot be fully used since pulse noise after a header pulse that detects a header region can erroneously be determined to indicate another header region, thus stopping data writing.
To solve the above problems, it is an object of the present invention to provide an apparatus and a method preventing data from being overwritten in a header region by removing noise having a narrow width in a signal detecting the header region. Further, it is an object of the present invention to prevent data from being overwritten in the header region when there are defects in the header region of the disc.
It is also an object of the present invention to provide an apparatus and a method to prevent data writing from being stopped when a data region is mistaken for a header region. In particular, it is an object of the present invention to prevent data writing in the data region from being stopped due to noise generated after a header pulse.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects, there is provided an apparatus protecting the header region of an optical disc write apparatus, comprising a pick-up reading a signal written on an optical disc, the signal being an RF signal, a write controller (an auto laser power controller (ALPC)) controlling the light intensity of the laser beam emitted from the pick-up by changing the light intensity of the write laser beam emitted from the pick-up corresponding to a write control signal to write a signal on the optical disc, and a write control signal generator controlling the write controller. The write control signal generator further includes a header region detector detecting a header signal included in the RF signal and a header protector generating write control signals to the write controller, such as the ALPC, and guarding against overwriting in the header region of the optical disc.
The header region detector includes a peak detector slicing an upper header signal included in the RF signal by a first voltage level and detecting a peak pulse, a bottom detector slicing a lower header signal included in the RF signal by a second voltage level and detecting a bottom pulse, a first window processor removing pulse noise having a narrow width, which is included in the peak pulse, a second window processor removing pulse noise having a narrow width, which is included in the bottom pulse, and an OR gating portion performing an OR operation on a peak signal that is the output signal of the first window processor and a bottom signal that is the output signal of the second window processor.
The header protector includes a write clock generator generating a write clock used as the reference clock of the write control signal generator, and a write stop signal generator generating a write stop signal compulsorily preventing generation of a write control signal. The write clock generator generating the write clock can be formed by using a crystal (X-tal) whose frequency is uniform and/or using a wobble signal detected from the RF signal.
The header protector further includes a counter counting the write clock and a count start signal detector starting the counting operation of the counter. The counter outputs a first state xe2x80x9cH,xe2x80x9d that is, a writing allowed state from a count start signal until the count value becomes a predetermined value, and a second state xe2x80x9cL,xe2x80x9d that is, a writing forbidden state by resetting the counter when the count value becomes a predetermined value. Also, since the counter is compulsorily reset by the write stop signal, the counter can output the writing forbidden state, that is, the state xe2x80x9cLxe2x80x9d before the counter value becomes the predetermined value. A count start signal detector demodulates the RF signal detected through the pick-up, detects physical identification data (PID) that is header information, and generates the count start signal from the PID.
The write stop signal generator includes a third window processor suppressing the write control signal for a predetermined period and an AND gating portion for performing an AND operation on the signal that passed through the third window processor and the header region signal detected by the header region detector.
Further, to achieve the above and other objects, there is provided a method of protecting the header region of an optical disc write apparatus reading through a pick-up a signal written on an optical disc, the signal being an RF signal, the method comprising changing the light intensity of the write laser beam emitted from the pick-up corresponding to a write signal, and writing a signal on the optical disc.
The method of protecting the header region of the optical disc write apparatus according to the present invention further includes detecting a header region from the RF signal detected from an optical disc through the pick-up, generating a write clock, generating a write control signal whose state is inverted after a lapse of a predetermined clock by counting the write clock, generating a write stop signal when the write control signal is generated in the header region signal section detected in the header region detecting, and controlling the light intensity of the write laser beam of the pick-up corresponding to the write control signal. In particular, as described in more detail below, the generating of the write stop signal comprises feeding the write control signal back to the generating of the write control signal to control the write control signal.
The header region detecting further comprises detecting a peak pulse by slicing an upper header signal included in the RF signal by a first voltage level, detecting a bottom pulse by slicing a lower header signal included in the RF signal by a second voltage level, removing pulse noise having a narrow width, which is included in the peak pulse, as a first window process, removing pulse noise having a narrow width, which is included in the bottom pulse, as a second window process and performing an OR operation on a peak signal output from the first window process and a bottom signal output from the second window process.
The write clock can be generated using a fixed crystal (X-tal) whose frequency is uniform and/or a wobble signal detected through the pick-up and a phase locked loop (PLL) circuit. The generating of the write clock further comprises detecting a count start signal to start the counting. In the counting, a first state xe2x80x9cH,xe2x80x9d that is, a writing allowed state is output until a count value becomes a predetermined value and a second state xe2x80x9cL,xe2x80x9d that is, a writing forbidden state is output by resetting the output when the count value becomes the predetermined value. In the counting, since the counter can be compulsorily reset responsive to the write stop signal, the counter can output the write stop state, that is, the state xe2x80x9cLxe2x80x9d before the output value becomes the predetermined value. In particular, the generating of the write stop signal comprises feeding the write control signal back to the generating of the write control signal to control the write control signal. The generating of the write stop signal further comprises suppressing the write control signal for a predetermined period as a third window process and performing an AND operation on the write control signal passed through the third window process and the header region signal detected in the header region detecting.
In the detecting of the count start signal, the RF signal detected through the pick-up is demodulated, the physical identification data (PID) included in the RF signal is detected, and the count start signal is generated from the PID.